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United States Patent |
5,090,394
|
Bruckelt
,   et al.
|
February 25, 1992
|
Distributorless ignition system
Abstract
A distributorless ignition system for an internal combustion engine
includes one spark coil for cylinder of the engine, a first reference
signal generator for producing a first signal indicative of each
revolution of the engine, a second reference signal generator for
producing a second signal indicative of every second revolution of the
engine, and a processor for evaluating the advance and dwell angles of an
ignition pulse to a selected spark coil determined from a logical
combination of the first and second signals. During starting, the
processor is arranged to operate in a dual-spark mode for the first
revolution of the engine and produce two ignition pulses simultaneously
for each first signal, one to each of two cylinders which are 360.degree.
out of phase with each other. During running of the engine, the second
reference signal generator is monitored and, if found to be faulty, the
processor changes from a one-spark mode to a dual-spark mode.
Inventors:
|
Bruckelt; Alfred (Steinheim, DE);
Kaiser; Gunther (Stuttgart, DE);
Krauter; Immanuel (Erbstetten, DE);
Ott; Karl (Markgroningen, DE)
|
Assignee:
|
Robert Bosch GmbH (Stuttgart, DE)
|
Appl. No.:
|
635138 |
Filed:
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December 28, 1990 |
PCT Filed:
|
June 16, 1989
|
PCT NO:
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PCT/EP89/00681
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371 Date:
|
December 28, 1990
|
102(e) Date:
|
December 28, 1990
|
PCT PUB.NO.:
|
WO90/15926 |
PCT PUB. Date:
|
December 27, 1990 |
Current U.S. Class: |
123/643; 123/630 |
Intern'l Class: |
F02P 005/15 |
Field of Search: |
123/179 BG,417,418,612,613,617,625,630,643
|
References Cited
U.S. Patent Documents
4044747 | Aug., 1977 | Longstaff | 123/643.
|
4265211 | May., 1981 | Meloeny | 123/643.
|
4432323 | Feb., 1984 | Iwasaki | 123/643.
|
4502441 | Mar., 1985 | Katayama et al. | 123/643.
|
4690124 | Sep., 1987 | Higashiyama | 123/179.
|
4711227 | Dec., 1987 | Li et al. | 123/643.
|
4960092 | Oct., 1990 | Sasaki et al. | 123/643.
|
4979487 | Dec., 1990 | Fukui | 123/643.
|
5042449 | Aug., 1991 | Dassetto | 123/630.
|
Primary Examiner: Wolfe; Willis R.
Attorney, Agent or Firm: Striker; Michael J.
Claims
We claim:
1. An ignition system for an internal combustion engine, comprising means
for generating a first signal indicative of a rotational position of the
engine; means for generating a second signal indicative of a further
rotation position of the engine; a plurality of ignition coils equal in
number to at least a part of the number of cylinders in the engine; and
computation means for computing and outputting ignition signals in
response to said first signal; said computation means being arranged to
address two cylinders of the engine at the same time and to apply an
ignition signal to an ignition coil or coils associated with each of said
two cylinders in the absence of a predetermined logical combination of
said first and second signals.
2. An ignition system according to claim 1, wherein the computation means
outputs ignition signals to said ignition coil or coils in response to
each said first signal during a first completed revolution of the engine.
3. An ignition system according to claim 1, wherein, at low engine speeds,
the ignition signal consists of a plurality of pulses.
4. An ignition system according to claim 1, wherein the computation means
further comprises means for monitoring operation of said means for
generating the second signal, and for detecting incorrect operation of
said second signal generating means.
5. An ignition system according to claim 4, wherein said monitoring means
indicates a plurality of different incorrect operations.
6. An ignition system according to claim 5, further comprising store means
for storing indications of the incorrect operations of said means for
generating the second signal.
Description
BACKGROUND OF THE INVENTION
The present invention relates to distributorless ignition systems for
internal combustion engines.
In an ignition system with non-rotary high-voltage spark distribution,
usually called a distributorless ignition system, and one ignition coil
per cylinder of the engine, it is usually necessary to provide two
reference signals in order to unambiguously distinguish each of the
cylinders. One of the reference signals is usually indicative of top dead
center (TDC) of number 1 cylinder and is derived from the crankshaft. The
other reference signal is required due to the fact that with a four stroke
cycle, for each cylinder there are two TDC positions but only one spark is
required. Consequently, a so-called "phase" signal is required which, when
logically combined with the TDC reference signal, indicates the
unambiguous position of the number 1 cylinder and hence each of the other
cylinders. This "phase" signal is usually derived from the crankshaft
every 720.degree. of crankshaft rotation.
It is absolutely necessary to check the phase signal at the start and
during engine operation for logical correctness (for example phase signal
present and not present in each case at successive reference marks, proper
angular position with respect to reference mark) since an incorrect phase
signal can lead to the drive to the ignition coils being offset by
360.degree. of crankshaft rotation and thus to an ignition of the mixture
in the exhaust phase. Since this diagnosis of the phase transmitter
requires monitoring of the reference mark transmitter and the phase
transmitter over at least 360.degree. of crankshaft rotation even at the
start of the engine before the first ignition is triggered, the starting
times are significantly extended.
The present invention provides an ignition system for an internal
combustion engine comprising means for generating a first signal
indicative of a rotational position of the engine, means for generating a
second signal indicative of a further rotational position of the engine, a
plurality of ignition coils equal in number to or a multiple of, the
number of cylinders in the engine, and computation means for computing and
outputting ignition signals in response to the first signal. The ignition
system according to the invention is characterized in that the computation
means is arranged to address two cylinders of the engine at the same time,
and to apply an ignition signal to a coil or coils associated with each of
the two cylinders in the absence of a predetermined logical combination of
the first and second signals.
This arrangement overcomes the disadvantage of extended starting times due
to the fact that sparks are generated during the first revolution of the
engine and until correct phasing of the ignition occurs. Should any fault
occur in the means for detecting the second (phase) signal while the
engine is running, it is possible to cause the processor to use the
control method normally used for dual-spark coils as this will permit the
engine to continue to operate although at some cost in terms of wear on
the spark plug.
In order that the present invention be more readily understood an
embodiment thereof will now be described by way of example with reference
to the accompanying drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a diagrammatic flow chart of a basic distributorless ignition
system;
FIG. 2 shows a timing diagram of the operation of the ignition system of
explaining the present invention;
FIG. 3 is a flow chart how the system of FIG. 1 operates to provide the
spark timings shown in FIG. 2; and
FIG. 4 is a flow chart explaining how the system of FIG. 1 operates during
running conditions.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In the embodiment to be described, only a non-rotary high-voltage
distribution ignition system for a four stroke engine will be described.
It is to be noted that the ignition system could be combined with another
system such as a fuel injection system.
Referring now to FIG. 1, a microcomputer-controlled ignition system
contains at least the circuit components of input interface (1),
microcontroller with on-board RAM/ROM and A/D converter (2) and output
interface circuits (3) for driving a plurality of ignition coils, one for
each cylinder. It is of advantage for workshop diagnosis of such ignition
systems if the microcontroller (2) is equipped with a permanent memory (4)
for permanently storing faults diagnosed during engine operation. Such a
permanent fault memory can be implemented, for example, with the aid of a
battery-buffered RAM or of an EEPROM or of a microcontroller with
power-down mode.
In this arrangement, the input interface circuits (1) have the task of
suitably editing the signals required for controlling the ignition time
and dwell angle such as speed of rotation, load, engine temperature,
intake air temperature, battery voltage, phase, switch signals and so
forth for the microcontroller.
In the case of the speed signal, the assumption is made, without
restricting the invention, that it is the known one-transmitter increment
Motronic system which enables speed and reference mark to be detected by a
single sensor. In the case of the phase signal, it is assumed in the
illustrative embodiment that it is generated by a Hall effect sensor
adjusted in such a manner that a signal is, generated by the Hall sensor
every 720.degree. of crankshaft rotation and coincides with a gap in the
speed signal. However, sensors operating in accordance with the most
varied principles such as, for example, in accordance with the inductive
transmitter principle, can be used a variation of the method and apparatus
described. The only prerequisite is that the phase signal exhibits a
particular period with respect to the crankshaft rotation when the sensor
is operating properly. In particular, the switching over of the ignition
system according to the invention between one-spark operation (with
correctly operating phase sensor) and two-spark operation (with faulty
phase sensor) is unaffected by this.
The microcontroller (2) measures the processed input signals in the known
manner and stores the instantaneous operating parameters of the engine,
obtained from these signals, in its RAM. Using the input parameters found,
the control program stored in the ROM of the microcontroller then
calculates the optimum ignition and dwell angle for any operational
condition of the engine with the aid of stored formulae, tables,
characteristics and families of curves. Conversion of the calculated
ignition and dwell angles into drive signals for the output interface
circuits (3) occurs in the microcontroller with the aid of integrated
timer/counter circuits.
The output interface circuits (3) provide the required current for the
ignition coils via appropriate output stages by means of the drive signals
supplied by the microcontroller.
When the system is started, the ignition system is always operated in a
so-called two-spark mode until proper operation of the phase sensor is
detected. In this mode, two ignition coils belonging to two cylinders
operating offset by 360.degree. of crankshaft rotation in the working
cycle are in each case driven at the same time; that is to say in each
case in the working cycle following the detection of the gap/reference
mark from the speed sensor, ignition of cylinder 1 and 3 is triggered and
180.degree. of crankshaft rotation later the ignition of cylinder 2 and 4.
This procedure corresponds to the method used when operating an ignition
system equipped with so-called dual-spark ignition coils and is shown in
FIG. 2 during period A.
If diagnosis of the phase signal shows proper functioning of the phase
sensor, the ignition system is operated in one-spark mode or switched over
from two-spark mode to one-spark mode. In this arrangement, the ignition
coils belonging to the individual cylinders of the engine are individually
and successively actuated in the ignition sequence depending on the
respective engine design (usual control method with non-rotary
high-voltage distribution with single-spark ignition coils). This is
represented by period B in FIG. 2. If a defect of the phase sensor is
detected during operation of the engine, the ignition system is operated
in two-spark mode again until the sensor is operating properly again.
The "start mode" and "normal mode" flow charts ar shown in FIGS. 3 and 4
respectively and describe by way of example for a four-cylinder engine the
monitoring procedures of the phase signal applied by the sensor, necessary
during the starting process and normal running engine operation, and the
switchover of the ignition system between one-spark mode and two-spark
mode, derived from the diagnosis of the phase signal.
Referring now to FIG. 3, after "ignition on" (switching device at battery
voltage or ignition switch), ignition systems usually detect commencement
of rotation of the engine driven by the starter by interrogating the speed
signal for a change of edge. To prevent wrong measurement of the engine
signals due to electrical interference in the on-board system during the
first starting phase, detection of the speed signal is normally suppressed
for a certain so-called de-bouncing time after detection of the first
speed signal edge and, after this time has lapsed, a certain number of
speed signal edges are counted until measuring of the engine signals
required for control of the ignition system is begun. From the measured
engine signals, the control program then calculates the engine operating
parameters and, using these, provides the variables "ignition angle" and
"dwell angle" required for driving the ignition coils. At this point, a
counter, (CHP), which is to be incremented later with each change of edge
of the phase signal, is reset, advantageously to zero.
The control program then begins with the synchronisation to the gap of the
speed transmitter signal (or of the reference mark search) which is
absolutely necessary for driving the ignition coils. This process is known
and, therefore will not be described in greater detail at this point. It
is necessary for the diagnosis of the phase sensor that during this
process each change of edge of the phase signal is registered via an
incrementation of the counter CHP.
The phase signal provides information indicating from which cylinder the
next ignition is to come. In other words, the phase sensor signal is
assigned to a certain cylinder and only occurs in the undisturbed state
once per 720.degree. of crank shaft revolution. When the phase sensor is
operating correctly, the relationship between the phase signal and the
speed signal is such that only one change of edge of the phase signal
occurs between any two successive reference marks in the speed signal, as
shown in FIG. 2. The reference mark is generated at a particular
crankshaft position, e.g.: top dead centre position at cylinder 1.
After the gap condition from the speed sensor has been satisfied, or the
reference mark detected, for the first time, the content of counter CHP is
evaluated to monitor the operation of the phase detector. With more than
one detected change of edge of the phase signal between two succesive
reference marks, it can be assumed that the phase sensor is not properly
operating and a clear assignment to a certain cylinder is not possible.
With two observed changes of edge of the phase signal, a maladjusted phase
transmitter can be assumed, with more than two changes of edge an
intermittent contact of the phase sensor or a disturbance of the signal,
for example by EM1 influences, can be assumed. Likewise if no phase signal
is detected (i.e.: the phase signal is always "high" or "low")
malfunctioning of the phase transmitter can be assumed. Again, assignment
to a certain cylinder is not possible.
If single faults of the system must also be stored in the permanent fault
memory, the observed malfunction can already be noted in the permanent
fault memory. If faults must occur several times before being entered in
the permanent fault memory, the observed malfunction is only registered in
a fault memory in the RAM of the CPU.
If only one or no change of edge of the phase sensor signal is observed, no
statement can yet be made about the proper functioning of the phase
transmitter.
However, independently of the outcome of this diagnosis, it is recommended
to operate the ignition system in two-spark mode during the first
crankshaft rotation and to decide only after the first crankshaft rotation
has been completed and the informative diagnosis of the phase signal is
then present, whether transfer to one-spark mode of the ignition system is
to be carried out. This is shown in FIG. 3.
FIG. 4 shows how the microcontroller is arranged to monitor the phase
sensor after the completed first crankshaft rotation of the fired engine
and during normal operation of the engine. The counter CHP must be reset,
preferably to zero, at the beginning of the monitoring routine of the
phase sensor (point A in FIG. 4). Each change of edge of the phase signal
will continue to be registered via an incrementation of the counter CHP.
After the gap condition has been satisfied, the count of counter CHP is
interrogated each time. With a correctly adjusted properly operating phase
transmitter, a single change of edge of the phase transmitter must be
observed within one specified crankshaft rotation (e.g.: cylinder 1 TDC to
cylinder 1 TDC). It is then possible to operate the ignition system in
one-spark mode or to switch over from two-spark mode to one-spark mode. In
this arrangement, the polarity of the signal of the phase transmitter,
measured during the satisfied gap condition, can be used for deciding
whether the ignition to be triggered in the next working cycle has to be
conducted to cylinder 1 or 3 (point B in FIG. 4).
If two changes of edge of the phase signal are observed within a single
crankshaft rotation, a mal-adjusted phase sensor must be assumed. The
ignition system is then logically operated in two-spark mode (point C in
FIG. 4). If no single change of edge of the phase signal is observed
within one crankshaft revolution, the phase sensor either has a short
circuit to earth or to battery voltage or the plug of the transmitter has
fallen out or the phase transmitter is mal-adjusted. The latter case can
be decided by observing the phase transmitter signal over two crankshaft
revolution. For this purpose counter L2 is used in an easily obvious
manner for counting the crankshaft roations. In each case, the ignition
system operation is continued in two-spark mode or switches from one-spark
mode to two-spark mode
If more than two changes of edge of the phase signal are observed within
one crankshaft revolution, an intermittent contact of the phase sensor
must be assumed. The ignition system is operated in two-spark mode.
The above system can be modified to use multiple ignition coils per
cylinder in which case each ignition coil of the multiple coils of each
cylinder can be controlled to operate separately or simultaneously.
Further, when the dwell angle is large at low speeds i.e. idling, rather
than a single ignition pulse, a series of short pulses can be applied to
the ignition coil or coils of each cylinder.
The above described embodiment of the inventions relies on the use of a
phase sensor signal which exhibits an "edge change" or change of state
between successive reference marks in the speed signal. However the use of
this type of signal is not essential to the invention.
The phase sensor may consist of a single short pulse once every 720.degree.
of rotation of the crankshaft. Such a signal might be derived, for
example, from a Hall sensor provided on the camshaft which operates the
intake and exhaust valves. The camshaft rotates at half the speed of the
crankshaft. In this case an alternative system according to the invention
may be used.
According to one such alternative system the operation of the phase sensor
is diagnosed in a single rotation or the camshaft of 720.degree.
crankshaft revolution. As mentioned above the phase signal provides
information indicating from which cylinder the next ignition is to come.
With correct operation of the phase sensor the signal occurs only once in
720.degree. of crankshaft rotation. The number of phase signals occuring
per 720.degree. rotation of the crankshaft is detected by suitable means
to test the operation of the phase sensor. Two different fault conditions
can be identified. More than one phase signal may be detected during
720.degree. of crankshaft rotation due, for example, to interence
affecting the phase line. In this case, a clear assignment to a certain
cylinder is not possible and, if the engine has just started, two-spark
mode is maintained or if the engine is running, the operation is switched
to two-spark mode. It is possible that no phase sensor signal will be
detected during 720.degree. of crankshaft rotation (signal always "high"
or "low"). Again no assignment to a certain cylinder is possible and
two-spark operation is maintained or switched in.
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